DE19816316A1 - Fuel injection device for internal combustion engines - Google Patents

Abstract

The invention relates to a fuel injection device for internal combustion engines, which supplies fuel injection valves (9), controlled by a control device (8), from a high-pressure fuel source (1). The fuel injection valve has an injection valve member (14), the opening or closing position of which is determined by a pressure acting on this injection valve member in a control chamber (24). For this purpose, the pressure in the control chamber (24) has to be relieved in order to carry out an injection, which is achieved with a control valve (31) which sequentially opens two different end cross sections of a discharge channel (49) of the control chamber (24) in succession. It is thus possible to bring about an adapted opening of the fuel injection valve member for a pre-injection and a main injection.

Description

State of the art

The invention relates to a fuel injection device for internal combustion engines according to the preamble of the patent claim 1 off. In such a case, by DE 196 24 001 A1 The known fuel injection device is the valve chamber in a first version without reducing the cross section connected to the control room. The control valve contributes Actuation by the piezo actuator to the drain cross section Drain channel either completely or closes it. In Another version is the valve chamber over a Connection channel connected to the control room, this Connection channel coaxial to the valve seat on the side of the Drain channel is. By operating the control valve member through the piezo actuator either the Drain cross-section from the valve chamber to the drain channel completely opened or closed or it is used to achieve a Pre-injection the control valve member from the valve seat to Drain channel away to the entry of the connecting channel in the valve chamber moves, as a result of this movement the control room for a short time via the valve room Drain channel is open. For a subsequent one The main valve injection into a control valve Moves middle position, in which both the cross section to  Drain channel out as well as the cross section of the Connection channel into the valve chamber fully open are. This configuration has the disadvantage that Relief of the pressure in the control room only one geometrically defined discharge cross-section to the discharge channel down there. The amount of pre-injection is in the second described embodiment so that the Adjustment speed of the control valve member by the Piezo actuator and the geometrically defined path of the Control valve member determining quantities for the degree of Relieve the pressure in the control room. In particular is the maximum relief cross section for both Relief for the pre-injection as well as for the Discharge for the main injection the same size, what for a fine tuning of the opening speed of the Injector in different operating conditions from Disadvantage is.

Advantages of the invention

The fuel injection device according to the invention with the characteristic features of claim 1 has against it the advantage that the control valve according to the invention sequentially two drain cross sections in succession are taxable. Thus a gradation of the Drain cross-section can be achieved depending on the stroke. Especially for low relief of the control pressure in the Control room can have a first smaller discharge cross-section come into effect with which the Pre-injection can be set. For the The main injection is then a large drain cross section available for a quick movement of the Injector member allowed. It is advantageous thereby a sleeve-shaped according to claim 2 Drag valve member provided that a second  Drainage cross section of the drainage channel controls if that Control valve member a first, relieving the control room Stroke. The one before the opening of the second Outflow cross section through the drag valve member Pressure reduction in the valve room or control room facilitates a quick opening of the second Drain cross-section in succession to the opening of the first discharge cross section at the first movement of the Drag valve member. This can be particularly fast Opening the injection valve member at the beginning of Main injection can be achieved.

In the further embodiment according to patent claims 3 to 5 are advantageous types of drain cross-section education suggested. To open the second Final cross section through the drag valve member can this advantageous according to claim 6 by a Driver on the control valve member from its main valve seat be lifted off. In an alternative embodiment according to Claim 8, the drag valve member can be advantageous also by a compression spring with a corresponding lowering of the Pressure in the valve chamber are moved to the open position, by lowering the pressure on the control valve member can follow. It is in an end position of the Control valve member of the discharge cross section through the Cross-section determined at the main valve seat. The design according to claim 9 provides accurate guidance of Drag valve member on the valve lifter. Furthermore, the This increases the guiding quality of the valve lifter be that according to claim 11 on the valve lifter a sleeve is provided, the outer diameter of which is larger than the diameter of the inner boundary surface of the Drag valve member. It is advantageous according to Claim 12 this sleeve after threading the Drag valve member pressed onto the plunger on this and  can then be installed as a whole. Claim 13 shows an alternative attachment of the sleeve on the Valve tappet. Further embodiments of the invention with their advantages are the following description in Take connection with the drawing.

drawing

Six exemplary embodiments of the invention are shown in the drawing and are explained in more detail in the description below. In the drawings Fig. 1 is a schematic representation of a fuel injector with the fuel supply from a fuel high-pressure accumulator and a fuel injection valve of a known type, Fig. 2 shows a first embodiment of the invention with a control valve member on which a drag valve member is arranged, which is moved away by a driver on the valve plunger from its valve seat is, Fig. 3 shows a modification of the embodiment of Fig. 2 with a control valve member having an improved guidance, Fig. 4 shows a third embodiment of the invention in a development from the embodiment of FIG. 2, instead of a driver for driving the tow valve member is a compression spring provided, Fig. 5 shows a fourth embodiment of the invention is provided in the drag on the valve member, a third valve seat, Fig. 6 shows a fifth embodiment with a control valve member which both the outflow cross section from the valve chamber to runoff ßkanal controls as well as the connecting channel between the valve chamber and control chamber, and Fig. 7 shows a sixth embodiment in which the control valve in an analogous embodiment to Fig. 2 controls the pressure of a control chamber with the aid of a 3/2-way valve design, a connection being unlockable from the valve chamber to the control chamber and coaxial to the control valve member, a high-pressure inflow to the control chamber is provided, which can be closed by an extreme position of the control valve member.

Description of the embodiments

A fuel injector with which at high Injection pressures a large variation with little effort the fuel injection with respect to the injection quantity and Injection time is possible is through a so-called Common Rail System implemented. This represents another Kind of high pressure fuel source available as it through the usual high pressure fuel injection pumps is given. However, the invention is also in principle conventional fuel injection pumps can be used. However, use with one is particularly advantageous Common rail injection system.

In the common rail injection system shown in FIG. 1, a high-pressure fuel reservoir 1 is provided as the high-pressure fuel source, which is supplied with fuel by a high-pressure fuel delivery pump 2 from a fuel reservoir 4 . The pressure in the high-pressure fuel reservoir 1 is detected by a pressure sensor 6 and fed to an electrical control device 8 , which controls the pressure in the high-pressure fuel reservoir via a pressure control valve 5 . The control device also controls the opening and closing of high-pressure fuel injection valves 9 , which are supplied by the high-pressure fuel reservoir for the injection of fuel.

In a known embodiment, the fuel injection valve 9 has a valve housing 11 , which has at one end, which is intended for installation on the internal combustion engine, injection openings 12 , the exit of which from the inside of the fuel injection valve is controlled by an injection valve member 14 . In the example shown, this is designed as an elongated valve needle, which at one end has a conical sealing surface 15 , which cooperates with an internal valve seat on the valve housing, from which the injection openings 12 lead away. The valve needle is guided in a longitudinal bore 13 at its top, the sealing surface 15 and is remote from the end remote from the sealing surface 15, 13 applied emergent end by a compression spring 18 in the closing direction of the longitudinal bore. Between the guide in the longitudinal bore 13 and the valve seat, the valve needle 14 is surrounded by an annular space 19 which opens into a pressure space 16 , which in turn is in constant communication with the high-pressure fuel reservoir 1 via a pressure line 17 . In the area of this pressure chamber, the valve needle 14 has a pressure shoulder 20 , via which the pressure in the pressure chamber 16 acts against the force of the spring 18 in order to lift the sealing surface 15 from the valve seat.

The valve needle is also acted upon by a tappet 21 , the end face 22 of which faces away from the valve needle 14 delimits a control chamber 24 in a tappet guide bore 23 . This is, is provided via an inlet duct 26 in which an inlet throttle 28, permanently connected to the pressure line 17 and the fuel high-pressure accumulator. 1 The inlet channel opens into the control chamber 24 so that it can not be closed laterally. A connection channel 29 leads from the control chamber 24 coaxially to the tappet 21 and opens into a valve chamber 30 of a control valve 31 . A diameter restriction, preferably in the form of a drain throttle 32, is provided in the connecting channel, which also represents a drain channel. The detailed structure of the control valve 31 is shown in more detail in the various exemplary embodiments 2 to 7. These exemplary embodiments have in common that the control valve 31 has a control valve member 34 , consisting of a valve tappet 35 , which is guided in a tappet bore 36 , and a valve head 37 at the end of the control valve member 34 projecting into the valve chamber 30 . At the end of the valve tappet 35 opposite the valve head, a spring plate 38 is provided, on which a compression spring 39 is supported, which strives to bring the control valve member into the closed position. In the opposite direction, the control valve member 34 is acted upon by a piston 40 , which is part of a piezo actuator 41 and, when the piezo is excited, can bring the control valve member into different open positions depending on the degree of excitation. The piston can be connected directly to the piezo of the piezo actuator or can be moved by the latter by means of a hydraulic or mechanical transmission.

For a more precise illustration of the configuration of the control valve 31 according to the invention, this is described in more detail with reference to FIG. 2. The end of the plunger 21 , which actuates the valve needle 14 , is again shown there. The plunger 21 includes in the lifter guide hole 23 with its serving as a movable wall face 22 of the control chamber 24 a. The adjustment of the plunger 21 is limited at the top by a stop 42 , which leaves an outer annular space 43 open, into which the inlet 26 opens. The connecting channel 29 , which contains the discharge throttle 32 and opens into the valve chamber 30, leads axially in the area of the stop 42 . This has a circular-cylindrical circumferential wall 45 which merges via a conical valve seat 46 into an annular space 48 surrounding the valve tappet 35 . From this, a drain channel 49 leads to a fuel return or a relief space.

The valve head 37 arranged at the end of the valve tappet 35 has a conical valve head sealing surface 51 which faces away from the entry of the connecting channel 29 into the valve chamber 30 and which cooperates with a valve seat 52 to form a valve 58 . This valve seat 52 is located at the transition to an inner through bore 53 of a sleeve-shaped drag valve member 54 which surrounds the valve tappet at a distance. The inner peripheral wall of the inner through bore 53 thus forms a passage cross section 56 together with the lateral surface 55 of the valve tappet 35 . To determine the position of the sleeve-shaped drag member 54 , it is guided over spacing ribs 57 on the valve tappet 35 . These ribs leave the adequately dimensioned passage cross section 56 free.

At the valve seat 52 axially opposite end, the sleeve-shaped drag member 54 has a valve member sealing surface 59 , which is also conical, with a smaller cone tip angle than the cone tip angle of the conical valve seat 46 and cooperates with the valve seat 46 . In this case, the conical valve seat 46 represents a main valve seat of a main valve 61 , which delimits a substantially larger passage cross section from the valve chamber 30 to the annular chamber 48 than the passage cross section which is limited between the valve head 37 and the valve seat 52 of the valve 58 . Furthermore, for better guidance of the sleeve-shaped drag valve member between this and the peripheral wall 45 of the valve chamber 30 , longitudinal ribs 60 are also provided with grooves in between, which leave a sufficiently large passage cross section 56 to the main valve 61 .

In Fig. 2, the control valve 31 is shown in the closed position, the valve head 37 with its sealing surface 51 has come to bear against the valve seat 52 and has brought the sleeve-shaped drag valve member 54 with its drag valve sealing surface 59 to bear on the main valve seat 46 , so that a connection between the valve chamber 30 and the annular chamber 48 or the drain channel 49 is prevented.

In this closed position of the control valve member, the control chamber 24 is held by the constant flow of high-pressure fuel quantities to the pressure of the high-pressure fuel reservoir 1 , which causes the plunger 21 to hold the injection valve member 14 in its closed position on the valve seat. This results from the fact that the area of the movable wall 22 is substantially larger than the area of the pressure shoulder 20 of the injection valve member 14 which is subjected to the same pressure. This high pressure in the control chamber 24 also acts on the valve head 37 and the sleeve-shaped drag member 54 in their respective closing directions.

To initiate an injection, the piezo actuator is actuated, which thereby adjusts the control valve member by an opening stroke. First, the pre-valve 58 is opened by the valve head 37 lifting off from the pre-valve seat 52 . A partial quantity of fuel can flow out to the drain channel 49 via the passage cross section 56 from the valve chamber or control chamber. Nevertheless, the pressure in the valve chamber 30 remains so high that the drag valve member remains with its valve member sealing surface in the closed position on the main valve seat 46 . Only when the stroke of the control valve member is so large that a driver 63, which for the valve tappet 35th B. is attached in the form of a U-shaped clamping element, comes into contact with the end face 64 of the sleeve-shaped drag valve member, this is lifted with the further movement of the valve tappet 35 from the main valve seat 46 , so that a larger discharge cross section is now released to relieve the valve chamber 30 or the control room 24 . When the excitation of the piezo actuator drops, the valve tappet 35 , together with the dragged sleeve-shaped drag valve member 54, returns to the starting closed position shown under the action of the spring 39 .

The great advantage of a piezo drive is the fact that a control valve member actuated by it can be brought into defined positions according to the excitation of the actuator. This means that injections can be easily and precisely divided into a pre-injection and a main injection. In the construction of the fuel injection valve presented above, only a slight relief of the control chamber 24 is required for a pre-injection such that the injection valve member only causes the injection openings 12 to open briefly. For a main injection, however, the control chamber 24 must be relieved quickly and effectively in order to carry out a large, rapid stroke of the injection valve member 14 . The faster the injection valve can open or close, the more precisely the injection phase can be determined. Because the inlet 26 contains the inlet throttle 28 and this is smaller than the cross section on the outflow side of the control chamber 24 , in particular the cross section of the outlet throttle 32 , the effective relief of the control chamber can be achieved. The control valve takes over the final control of the cross section towards the drain channel 49 . This must first work against the high pressure in the control chamber 24 or in the valve chamber 30 . However, since the discharge cross section at the pilot valve 58 is small in relation to the main valve 61 , relatively little work is required to open the pilot valve 58 . By opening the pilot valve, the pressure in the valve chamber 30 is already significantly reduced, so that when a larger wall pressurized by the pressure in the valve chamber 30 has to be adjusted against this pressure, the force applied is already lower. With this lower force than that required for one-step opening, the cross-section of the main valve is opened quickly, which leads to a correspondingly quick relief of the valve chamber and control chamber. The control valve can be controlled in such a way that when the pilot valve 58 is opened, the pressure in the control chamber 24 is already lowered so that a short opening stroke of the injection valve member 14 is made possible. Subsequently, the control valve member 35 can be moved on again and control the larger discharge cross-section via the drag valve member 54 in order to initiate the opening of the injection valve member 14 for the main injection with the subsequent rapid relief. The termination of the main injection is controlled by closing the control valve and thus also the injection quantity.

In an alternative embodiment of the control of the control valve according to the invention, the pressure after the opening of the pilot valve can only be relieved to the extent that the injection valve member 14 remains closed, but only a slight further relief causes the same to open. A subsequent further adjustment of the valve tappet 35 can then be followed by a brief further relief of the pressure in the control chamber 24 or valve chamber 30 by increasing the degree of opening of the pilot valve and / or by dragging the drag valve member to produce a pre-injection and then by reducing the valve tappet stroke an end to the same. This is then followed by a larger valve tappet stroke, in which a complete relief of the control chamber 24 for carrying out the main injection is in turn effected via the drag valve member 54 .

With the help of the stroke h1 of the valve tappet 35 , which is necessary so that the driver 63 comes to rest against the end face 64 of the drag valve member 54 , the opening stroke of the pilot valve can be defined. The end face 64 is designed so that the sufficient passage cross section 56 from the valve chamber 30 to the annular chamber 48 is available even when the annular driver 63 is in contact. The end face can be designed, for example, in a crown-like manner, with radial passage cross sections. The limitation of the outlet cross section by the outlet throttle 32 , which in the example shown is arranged in the connecting channel 29 , can also follow at another point, for example in the outlet channel 49 or by dimensioning a maximum flow cross section 56 in between.

Figs. 8a to 8c are shown the control procedures of this control valve. In Fig. 8a of the stroke of the injection valve member 14 is applied or the time via the angle of rotation of the internal combustion engine. One recognizes the smaller pre-stroke V of the injection valve needle 14 for performing the pre-injection, the intermediate pause P, in which the control valve is closed completely or to the extent that a pressure in the control chamber 24 which brings the injection valve member back into the closed position, and the subsequent stroke H , the duration of which the main injection is defined. This is triggered by the strokes of the control valve member shown in the sequence below. One recognizes the stroke V1, through which the control chamber 24 is relieved when the maximum opening position at stroke h1 of the tappet 35 is reached , for example before the drag valve member is lifted from the main valve seat, so that the stroke of the injection valve member 14 for the stroke V can begin. Via the stroke VI, the relief to the pre-injection remains. During the actuation pause P1 of the control valve member, ie when the piezo is not energized, the injection valve member 14 remains closed. At the end of P1, the control valve member 35 is re-actuated by the piezo up to a stroke h2, in which the entire control cross-section is opened by the drag valve member 54 after the main valve 61 is opened and the control chamber 24 is maximally relieved. The injection valve member opens already in the range between h1 and h2 and remains in the open position over the length of the control valve being open until the pressure in the control chamber 24 falls below the closing movement of the control valve member, which pressure is able to keep the injection valve member open.

The diagram 8 c below shows the pressure curve in the control chamber 24 with corresponding pressure drops when the control valve member h1 has opened according to diagram 8 b.

A modification of the control valve according to FIG. 2 is shown in FIG. 3. To the extent that this configuration corresponds to FIG. 2, the same reference numbers are used. For this, reference is made to the corresponding description of FIG. 2. Deviating from the embodiment according to FIG. 2, in Fig. 3 in the region of the valve tappet is guided in the tappet bore 36 135 in which at Fig. 2, a sleeve disposed on the plunger 166 135th In Fig. 3, this sleeve is axially fixed between a stop 167 and a retaining washer 168 on the tappet. The stop is formed by a shoulder of the tappet, which is provided at the end of the spacer ribs 57 protruding from the sleeve-shaped drag member 54 . The retaining washer can be implemented, for example, as a snap ring in an annular groove 69 in the tappet at its end protruding from the tappet bore 136 . Alternatively, however, the sleeve can also be pressed onto the plunger 135 . The stroke h1 is also defined by the stop 167 , from which the tappet, which moves together with the sleeve 166 , comes to bear against the sleeve-shaped drag member 54 . Furthermore, the sleeve 166 has a diameter reduction at its lower end facing the drag valve member 54 , with which an annular space 148 is formed here in replacement of the annular space 48 of FIG. 2 and is constantly connected to the drain channel 49 . As in the previous exemplary embodiment according to FIG. 2, the drag member 54 is designed on its end face in such a way that an overflow cross section is left which is in the order of magnitude of the passage cross section 56 .

With this configuration, there is the advantage that the guide surface within the tappet bore 136 is larger and thus the control valve member is guided more precisely. Since the plunger 135 must be passed through the inner through-bore 53 for assembly, an increase in the guide diameter of the plunger in the region of the plunger bore according to FIG. 2 would actually be a limit. By adding the sleeve 166 , the guide surface can nevertheless be enlarged, the sleeve being subsequently mounted on the valve tappet after threading the drag valve member 54 . The outer diameter of the sleeve is larger than the diameter of the inner through bore 53 of the drag valve member and smaller than the diameter of the valve chamber 30 .

Another variant of a control valve in a modification of the exemplary embodiment according to FIG. 2 is shown in FIG. 4. Here, too, two different discharge cross sections of the discharge channel are opened in succession. As in FIG. 2, the control chamber 24 delimited by the plunger 21 of the injection valve member 14 is again provided, which is connected to the valve chamber 30 via the connecting channel 29 containing the throttle 32 . The tappet 235 with the valve head 237 and the valve head sealing surface 251 , which is in contact with the valve seat 52 of the sleeve-shaped drag valve member 54 in the closed state of the control valve, projects into this valve chamber, forming the valve 58 . Via the valve head 237 , this is additionally held with its valve member sealing surface 59 in contact with the main valve seat 46 of the main valve 61 . Beyond this valve seat 46 is again the annular space 48 , which is penetrated by the plunger 235 and which is in constant communication with the outlet channel 49 . As in the exemplary embodiments according to FIGS. 2 and 3, the sleeve-shaped drag valve member 54 is guided on its outer circumference via longitudinal ribs 60 , which are formed by grooves lying between them, on the peripheral wall 45 of the valve chamber 30 . These longitudinal ribs leave the flow cross section to the main valve 61 free. The inner through bore 53 of the drag valve member 54 is spaced from the valve tappet 35 , so that, starting from the pre-valve, there is a corresponding flow cross section 56 to the annular space 48 or drainage channel 49 .

The connecting channel 29 lies coaxially opposite the valve head 237 and opens there in an axial boundary wall 270 of the valve chamber 30 . Opposite the mouth of the connecting channel 29 , the valve head 237 is provided on its end face with a sealing surface 271 , which can either be conical or conical. Accordingly, the area of the outlet of the connecting channel 29 on the axial boundary wall 270 is designed as a valve seat, so that the connecting channel can be closed by the sealing surface 271 . The axial boundary wall is thus designed as a valve seat of a third valve 279 with the valve head 237 as a valve member.

In this valve, the actuation of the valve tappet 235 follows such that the valve head 237 is moved away from its contact with the valve seat 52 in one go in order to achieve a pre-injection, until its sealing surface 271 contacts the valve seat 270 of the third valve 279 or on the axial boundary wall 270 . The valve head 30 and the control chamber 24 are relieved for a short time via the path of the valve head, which, given the appropriate dimensioning, is sufficient to cause the injection valve member 14 to open in order to carry out a pre-injection. If the valve head 237 lies with its sealing surface 271 close to the axial boundary wall 270 , i.e. if the connecting channel 29 is completely closed, the pressure in the valve chamber can further relax, during which time the pressure in the control chamber 24 is built up again via the inlet 26 , which is a Closing of the injector needle 14 follows. The pressure relief in the valve chamber 30 in turn results in that the return forces, arranged in the annular chamber 48 compression spring 272 which bears between the housing and the annular chamber-side end of the tow valve member 54 prevails and the tow valve member 54 to move the valve head 237 readjusts to turn tight contact on its valve head sealing surface 251 . If the valve head is subsequently moved to an intermediate position between the valve seats 270 and 46 by appropriate control of the piezo actuator, the control chamber 24 can be relieved very quickly to the fullest extent possible via the valve chamber 30 and the large opening cross section of the main valve 61 , so that here a maximum, rapid adjustment of the injection valve member in the opening direction can be carried out for carrying out a main injection. The decoupling of the control chamber 24 from the pressure source 1 via the inlet throttle 28 allows relief to almost complete relief pressure, favored by the large outflow cross section on the outer circumference of the drag valve member. To end the main injection, the valve head is returned together with the drag valve member 54 , with the pilot valve 58 and the main valve 61 sealed. The great advantage of this configuration is that only one movement of the control valve member in one direction is required to carry out the pilot injection and only one return movement in the form of a partial stroke in the direction of the starting position and a subsequent final return for carrying out the main injection.

While only two valves were implemented in connection with the control valve member and the drag valve member in the exemplary embodiments FIGS. 2 and 3, a total of three valves were implemented in the above-described exemplary embodiment FIG. 4, the pilot valve 58 with the pilot valve seat 52 , the main valve 61 with the main valve seat 46 and the third valve 279 with the valve seat 270 . In an alternative embodiment according to FIG. 5, three valves are also implemented here. However, this embodiment builds on the configuration according to FIG. 3. As in FIG. 3, the valve chamber 30 is also provided here, in which the connecting channel 29, coming from the control chamber 24 , opens coaxially to the valve tappet 35 .

Here again the valve head 337 is provided on the end of the tappet 335 projecting into the valve chamber 30 , with the valve head sealing surface 351 , which cooperates with the valve seat 52 on the drag valve member 354 to form the valve 58 . At its end facing away from the valve head 337, this in turn has a conically inclined or spherical arrangement of the valve member sealing surface 59 , which cooperates with the main valve seat 46 to form the main valve 61 at the transition between the valve chamber 30 and the annular chamber 48 . The drag valve member is guided on the outer circumference by longitudinal ribs 60 on the circumferential wall of the valve chamber. A sleeve 366 is also pressed onto the valve tappet 335 and has an enlarged outer circumference over which the valve tappet is guided in the tappet bore 336 . This sleeve 366 protrudes into the annular space 48 connected to the drain channel 49 and projects there over an annular groove 374 of the tappet 335 , which is axially limited by the valve head sealing surface of the valve head 337 and maintains the radial distance from the inner through bore 53 of the drag member 54 and thus the flow cross section 56 forms. The sleeve 366 now has in its area overlapping the annular groove 374 on the end face a conical sealing surface 375 , which can be brought into contact with a conical valve seat 376 on the end face of the drag valve member 354 by corresponding movement of the valve tappet 335 . This valve seat 376 thus forms a third valve 379 together with the conical sealing surface 375 . The conical valve seat 376 is inclined toward the inside of the inner through bore 53 of the drag valve member 354 , that is to say in the opposite direction to the inclination of the valve member sealing surface 59 of the main valve 61 .

In the closed position of the control valve shown, the valve head with its valve head sealing surface is brought into contact with the valve seat 52 and the drag valve member 354 with its valve member sealing surface 59 is brought into contact with the main valve seat 46 . The connection between the valve chamber 30 and the drain channel 49 is thus prevented and the control chamber 24 can be brought to the high pressure specified by the pressure source, with the success of the closing of the injection valve member 14 . When the control valve is subsequently actuated to carry out a pilot injection, the tappet 335 with the sleeve 366 is moved so far that the conical sealing surface 375 of the sleeve 366 comes into tight contact with the conical valve seat 376 of the drag valve member 354 . A brief relief of the valve chamber 30 and the control chamber 24 takes place via this stroke h5, which is sufficient to move the injection valve member 14 into a pre-injection position. When the third valve 379 is closed by the sealing surface 375 bearing against the conical valve seat 376 after the stroke h5 has been covered, the pre-injection is ended by pressure build-up in the control chamber 24 . The control valve member is subsequently moved for the main injection. As a result, the drag valve member 354 is lifted off the main valve seat 46 , so that there is a full maximum relief of the control chamber 24 . A substantially larger cross-section is available for this relief than that available for carrying out the pilot injection, by opening the pilot valve until the third valve closes. The advantage of this configuration is that a staged energization of the piezo actuator must be switched in only one direction for the pre and main injection. This results in very short switching times, in particular by switching from one valve seat 52 to the other valve seat 376, a very short relief and thus a very small pre-injection quantity can be achieved. To end the injection, the plunger is returned to the starting position shown. A separate relief cross-section is available for each injection process and can be adapted to the corresponding requirements.

A fifth exemplary embodiment of the invention is shown in FIG. 6, which represents a further development of the exemplary embodiment according to FIG. 4. As in the exemplary embodiment according to FIG. 4, three valves are realized in cooperation with valve head 437 and drag valve member 454 . As in FIG. 4, the connecting channel 29 opens into the valve chamber 30 coaxially with the valve tappet 435 . As in the exemplary embodiment according to FIG. 4, the axially directed wall 470 of the valve chamber 30 at the entry of the connecting channel 29 is designed as a valve seat of the third valve 479 , against which the end face 471 of the valve head 437, which is designed as a sealing surface, can be brought into contact. The valve head 437 carries the valve head sealing surface 51 , which cooperates with the valve seat 52 at the transition from the end face of the drag valve member 454 to its inner through bore 53 to form the valve 58 . At the opposite end, the drag valve member 454 carries a conical valve member sealing surface 459 which cooperates with the main valve seat 46 at the transition from the valve chamber 30 to the annular chamber 48 to form the main valve 61 . As in the embodiment of FIG. 4, the drag valve member 454 is loaded by a compression spring 472 in the direction of opening the main valve 61 . The spring 472 attaches to a nozzle-shaped extension 478 of the drag valve member 54 via a thrust washer 477 . In the area of this nozzle-shaped extension 478 , the drag valve member 454 is guided tightly on the outer jacket 455 of the valve tappet 435 , so that an annular recess 480 is enclosed between the valve head 437 and the drag valve member 454 , which is in constant communication with a throttle bore 481 leading through the drag valve member the annular space 48 .

In this embodiment, three throttles are thus realized, firstly, the inlet throttle 28 in the inlet 26 to the control chamber 24 , secondly, it is the outlet throttle 32 in the connecting channel 29 and thirdly the above-mentioned throttle bore 81 .

As in the exemplary embodiment according to FIG. 4, the control valve member is actuated in order to achieve a pilot injection in such a way that the valve head 437 is lifted from the pilot valve seat 52 and moved through until its sealing surface 471 abuts the valve seat 470 of the third valve 479 . Over this period of movement there is a short relief of the control chamber 24 , which is determined by the cross section of the throttle bore 481 as the only connection between the control chamber 24 and the annular chamber 48 with the drag valve member initially still resting on the main valve seat 46 . Then in the closed position of the third valve 479 in contact with the axial boundary wall 470 of the valve chamber 30 , the valve chamber is further relieved via the throttle bore 481 . This creates a relief pressure in the valve chamber 30 , which allows the drag valve member 454 to be moved by the spring 472 away from the main valve seat 46 to bear against the valve head sealing surface 51 of the valve head. However, this also opens the main valve 61 , so that the control chamber 30 can continue to be relieved. To carry out the main injection, the valve head 437 is then moved together with the drag valve member 454 into an intermediate position in which the large connecting cross section of the main valve 61 between the drain channel 49 and the control chamber 24 is open.

In contrast to the embodiment according to FIG. 4, there is the possibility here of using throttles in a targeted manner to determine the relief dynamics of the control chamber 24 . In order to carry out the pilot injection, the relief is determined by the throttle bore 481 and in the main injection the relief of the control chamber 24 is determined by the larger discharge throttle 32 , which is smaller than the outflow cross section of the main valve 61 . Together with the supply throttle 29 then turns on the definition of the main injection in the desired gradation of the pressure in the control chamber 24 a. The main injection is finally achieved by moving the plunger 435 back into the starting position shown in FIG. 6, in which the pilot valve 58 and the main valve 61 are closed and the third valve 479 is open. In this way, the tolerance influence of the valve stroke can be minimized in the end stroke area of the valves. The cross sections can be individually adapted for the pre and main injection.

The diagram in FIGS. 9a to 9c shows how the movement sequences of the injection valve needle 14 , the valve head 437 and the drag valve member 454 are designed. In the above diagram 9 a, the movement of the injection valve needle is recorded over the stroke and the time, with a small stroke for pre-injection V, an intermediate pause P, in which the injection valve is closed and a subsequent main injection H. The pre-injection is triggered according to 9 underlying diagram b by the movement of the valve head 437th Starting from the closed position according to FIG. 6, the valve head is moved through from the valve seat 52 until it abuts the valve seat 470 of the third valve, which is represented in the diagram by the number 470 on the ordinate. At this point in time, the control chamber 24 is closed again, so that the high closing pressure in the control chamber 24 is set and the injection valve member 14 is kept closed via the pause in which the third valve 479 is also closed. During this period, however, according to diagram 9 c, the drag member 454 moves from closing the third valve 479 until it abuts the valve head 437 . This position is shown in the diagram with the number 52 on the abscissa. After contact, the drag valve member 454 also remains in this end position until the end of the pause P. Then the control valve member is moved back into an intermediate position. Here, the valve head 437 and the drag valve member move synchronously into an intermediate position Z, which leads to the complete relief of the control chamber 24 . With the return of valve head 437 and drag valve member 454 , the relief of the control chamber 24 is finally interrupted again and the control pressure which causes the injection valve member to close is built up again.

In the above, various embodiments of the control valve have shown that a connection to the drainage channel 49 is established in order to control the pressure in the control chamber 24 , which relieves the pressure on the control chamber 24 . To load the control chamber, only the control valve is brought back into the closed position and the constant supply of high fuel pressure via the supply channel 26 is set. In principle, such valves work as 2/2 valves. In the present, such a 2/2 valve was modified by the drag valve member 54 . According to Fig. 7, such a valve can, however, also be designed as a 3/2-valve, whereby a connection from the fuel high-pressure accumulator prepared in a first position of the valve from the control space with simultaneous closure of the drain channel and in a second position of the valve the connection between the fuel high-pressure accumulator 1 and control room are prevented, establishing the connection of the control room to the relief channel. Fig. 7 shows in this regard a very similar configuration as Fig. 2 with the difference that the valve chamber 530 is in constant connection with the not shown here, the control chamber via the connecting passage 529th This connecting channel branches off from the circumferential wall of the cylindrical valve space 530 . High-pressure fuel is fed in here on the axial end wall 570 of the valve chamber 530 , this inflow 526 opening out coaxially with the axis of the valve chamber 530 or the plunger 535 . The end face 570 forms in the mouth area of the inlet 526 a valve seat which interacts with an end sealing surface 571 on the valve head 537 in an analogous configuration to FIG. 4 as a third valve 479 , but here in a different function. As in the previous exemplary embodiments, the valve tappet 535 is guided in a tappet bore 36 and penetrates the annular space 48 , which in turn merges with the larger valve chamber 530 via the main valve seat 46 . With the main valve seat 46, a valve member sealing surface 59 acts a similarly to Fig. 2 T-valve member 54 formed together, said valve member sealing surface is conical, the conical transition between valve chamber 530 and annular space 48 and at one end of the sleeve-shaped dragging the valve member 54 similarly inclined to the outer periphery arranged is. At the opposite end of the sleeve-shaped valve member 54 there is in turn inclined to the inner through-bore 53 a conical valve seat 52 , which cooperates with a valve head sealing surface 551 , which is also conical, on the valve head 537 . In the area of the annular space 48 , the valve tappet 535 also has a driver 563 , which can be clipped into an annular groove 583 of the valve tappet, for example as a snap ring. If the valve head is in contact with the valve seat 52 of the valve 58 and the valve member sealing surface 59 is in contact with the main valve seat 46 of the main valve 61 , the driver 563 is spaced apart by a stroke h1 from an end face 564 of the drag valve member. Even when the driver 563 is in contact with the end face 564 , sufficient cross section remains to allow a fuel flow to flow from the valve chamber 530 when the pilot valve is open through the passage cross section 56 formed between the valve tappet 535 and the inner through bore to the annular chamber 48 and from there via the drainage channel to the relief side.

When the valve tappet 535 is actuated by the actuator, it can be lifted with the valve head from the valve seat 52 , so that with the simultaneous inflow of fuel via the inlet channel 536 and outflow of fuel via the passage cross section 56 to the outlet channel 49 , an average pressure is established in the control chamber, which is sufficient to effect a pre-injection by opening the injection valve member 14 . For the main injection, the control valve member is switched through with the valve head 537 until the sealing surface 571 bears on the valve seat 570 or the third valve 579 closes. This prevents the inflow of high-pressure fuel into the valve chamber and thus also into the control chamber, and the control chamber can be completely relieved of the drainage channel 49 . In the course of this movement, the driver 563 additionally comes into contact with the end face 564 and has lifted the drag valve member 54 from the main valve seat 46 , so that a very large relief cross section from the control chamber 24 to the drainage channel 49 is also produced. To end the main injection, the valve tappet with valve head 537 is then moved back into the starting position shown, in which the third valve 579 is opened and the pilot valve 58 and the main valve 61 are closed. It can then build up again by the incoming high pressure fuel, the high pressure in the control room and bring the injection valve member 14 in the closed position. In an analogous manner, the configurations according to FIGS. 3 and 5 can also be used analogously with such a 3/2 control valve.

Claims (22)

1. Fuel injection device for internal combustion engines with a high-pressure fuel source ( 1 ), from which a fuel injection valve ( 9 ) is supplied with fuel, which has an injection valve member ( 14 ) for controlling an injection opening ( 12 ) and a control chamber ( 24 ) from a movable wall (22) which is connected at least indirectly to the injection valve member (14) is limited and which has a from a high pressure source, preferably from the high-pressure fuel source (1) coming feed channel (26), and a leading to a relief space outflow duct (29), and the pressure thereof is controlled by a control valve ( 31 ) which controls the inflow channel ( 26 , 126 ) or the outflow channel ( 29 , 49 ) and is actuated by a piezo actuator ( 41 ), the control valve ( 31 ) being a control valve member ( 34 ) has with a valve tappet ( 35 ) guided in a housing, at the end of which a valve k projecting into a valve chamber ( 30 ) Opf ( 37 , 137 ) is provided, which has a valve head sealing surface ( 51 ) facing a valve seat ( 52 ) and which controls a discharge cross section of a discharge channel ( 49 ), the valve chamber ( 30 , 130 ) being connected to the control chamber ( 24 ) and is exposed to the pressure of the high-pressure fuel source ( 19 ) when the discharge cross-section is closed, characterized in that two control cross-sections of different sizes can be opened in succession by the control valve. 2. Fuel injection device according to claim 1, characterized in that within the valve chamber ( 30 , 530 ) the valve tappet ( 35 ) is surrounded by a sleeve-shaped drag valve member ( 54 ) with an inner boundary surface ( 53 ) between the and the valve tappet ( 35 , 135 ) has an inner passage cross section ( 56 ) and the drag valve member ( 54 ) has at its one axial end to the side of the valve head sealing surface ( 51 ) a valve seat ( 52 ) which forms a valve ( 58 ) together with the valve head sealing surface ( 51 ), the controls a first discharge cross-section connected to the discharge channel ( 49 ) via the inner passage cross-section ( 56 ) and has at its other axial end a valve member sealing surface ( 59 ) which interacts with a main valve seat seat ( 46 ) fixed to the housing, forming a second discharge cross-section of the discharge channel) controlling main valve ( 61 ), downstream of that of the Abfl usskanal ( 49 ) continues. 3. Fuel injection device according to claim 2, characterized in that there is an outer passage cross-section to the main valve seat ( 46 ) between the wall ( 45 ) of the valve chamber ( 30 ) and the drag valve member ( 54 ). 4. Fuel injection device according to claim 3, characterized in that the main valve seat ( 46 ) is formed at the transition of the valve chamber ( 30 ) to an annular space ( 48 ) penetrated by the valve tappet ( 35 ), from which the drainage channel ( 49 ) continues. 5. Fuel injection device according to claim 4, characterized in that the control valve member ( 34 ) by the piezo actuator ( 41 ) is movable by defined strokes and upon actuation of the control valve member ( 34 ) to relieve the pressure in the valve chamber ( 30 ) over the first discharge cross-section of the Drain channel at a first stroke, the valve head sealing surface ( 51 ) of the pilot valve ( 58 ) is lifted from the pilot valve seat ( 52 ) and with a subsequent further stroke of the control valve member ( 34 ), the drag valve member ( 54 ) is lifted from the main valve seat ( 46 ) and the second discharge cross section of the Drain channel ( 49 ) is opened. 6. Fuel injection device according to claim 5, characterized in that the drag valve member ( 54 ) is lifted by a driver ( 63 ) arranged on the control valve member ( 34 ) from the main valve seat ( 46 ). 7. A fuel injector according to claim 6, characterized in that the driver ( 63 ) is a ring inserted into an annular groove of the tappet ( 35 ), which, when the pilot valve ( 58 ) is closed, defines a distance h1 defining a pilot stroke from the end face ( 64 ) of the drag valve member ( 54 ) has. 8. Fuel injection device according to claim 5, characterized in that the drag valve member ( 54 ) by a housing-fixed supporting spring ( 272 , 472 ) to the valve head sealing surface ( 251 , 451 ) is loaded and after opening the pilot valve ( 58 ) and corresponding pressure reduction upstream of the pilot valve away from the main valve seat ( 46 ) to the valve head sealing surface ( 251 , 451 ) and this is tracked. ( Figs. 4 and 6) 9. Fuel injection device according to claim 6 or 7, characterized in that the drag valve member ( 54 ) by means of longitudinal spacing ribs ( 57 ) from the adjacent plunger ( 35 ) is spaced and guided to form the inner passage cross section. 10. Fuel injection device according to claim 6, 7 or 9, characterized in that the drag valve member ( 54 ) on its outer circumferential surface has longitudinal spacing ribs ( 60 ) by means of which it on a cylindrical peripheral wall ( 45 ) of the valve chamber ( 30 ) to form the outer passage cross section is led. 11. Fuel injection device according to one of the preceding claims 2 to 10, characterized in that the valve tappet ( 135 , 335 ) is provided in the region of its part leading away from the annular space ( 48 ) and guided in the housing with a sleeve ( 166 , 366 ), the outer diameter of which is larger than the diameter of the inner boundary surface ( 53 ) of the drag valve member ( 54 ). ( Figs. 3 and 5) 12. Fuel injection device according to claim 11, characterized in that the sleeve ( 166 , 366 ) is pressed onto the valve lifter ( 135 , 335 ). ( Fig. 3) 13. Fuel injection device according to claim 11, characterized in that the on the valve tappet (135) is clamped in the sleeve (166) between a fixed outside its guide on the valve plunger retaining disc (168) and a stop (167) on the valve tappet (135). ( Fig. 3) 14. Fuel injection device according to claim 8, characterized in that the drag valve member ( 54 ) with a cylindrical inner boundary surface ( 453 ) on the cylindrical outer jacket ( 455 ) of the plunger ( 435 ) is guided and in the overlap area of the inner boundary surface with the outer jacket of the plunger ( 435 ) an annular recess ( 480 ) is provided which is in constant connection with the annular space ( 48 ). ( Fig. 6) 15. Fuel injection device according to one of claims 11 to 13, characterized in that a sealing surface ( 375 ) is provided on the end face of the sleeve ( 366 ) and the opposite side of the drag valve member ( 354 ) also has an additional sealing surface ( 376 ), which sealing surfaces together form a third valve ( 379 ) which opens to the inner passage cross section and which is closed when the valve tappet ( 335 ) has completed its stroke to open the first discharge cross section of the pilot valve ( 58 ). ( Fig. 5) 16. Fuel injection device according to claim 15, characterized in that the sealing surfaces of the third valve ( 479 ) are conical. ( Fig. 5) 17. Fuel injection device according to one of the preceding claims, characterized in that the control chamber ( 24 ) via a supply throttle ( 28 ) is continuously connected to the high pressure source ( 1 ), the flow cross section of the supply throttle being smaller than the first discharge cross section ( 32 ) of the discharge channel ( 29 , 49 ) 18. Fuel injection device according to claim 17, characterized in that the effective discharge cross section of the discharge channel ( 49 ) is limited by a discharge throttle ( 32 ). 19. Fuel injection device according to claim 17 or 18, characterized in that the control chamber ( 24 ) via a coaxial to the axis of the valve tappet ( 35 ) discharging connection channel ( 29 ) is connected to the valve chamber ( 30 ). 20. Fuel injection device according to claim 19, characterized in that the outlet of the connecting channel ( 29 ) into the valve chamber ( 30 ) from the control chamber through an end face ( 271 , 471 ) of the valve head ( 235 , 435 ) of the control valve ( 231 ,) 431 ) can be closed and is closed at the end of the pilot stroke of the control valve member after a period of relief of the control chamber ( 24 ) determined by the actuating movement of the control valve member. ( Figs. 4 and 6) 21. Fuel injection device according to claim 20, characterized in that the discharge throttle ( 32 ) is arranged in the connecting channel ( 29 ). 22. Fuel injection device according to one of claims 1 to 16, characterized in that the valve chamber ( 530 ) via a coaxial to the axis of the valve lifter ( 535 ) in the valve chamber ( 530 ) entering pressure channel ( 526 ) with the high-pressure fuel accumulator ( 1 ) and via Unlockable connecting channel ( 529 ) is connected to the control chamber, the entry of the pressure channel ( 526 ) into the valve chamber through an end face ( 571 ) of the valve head ( 537 ) of the control valve member designed as a sealing surface at the end of the relief of the control chamber ( 530 ) for pre-injection Serving stroke of the control valve member is closable, to determine the start of the relief of the control chamber for the main injection. ( Fig. 7)